High-traction footwear tread



Jan. 30, 1962 'r. H. DOHERTY HIGH-TRACTION FOOTWEAR TREAD Filed July 11, 1960 M l llll fzhl '"irml Mini III

BY G 74mm AGENT ,0 ,5 1 HI H- RAC I N Q T TREAD Thomas H. Doherty, South Bend, Indl, assignor to Mishawaka Rubber Company, Inc., Mishawalra, 11111., a corporation "of Indiana Filed July 11, 1%0, Ser. No. 42,002

14 Claims. (Cl. 36-59) This invention relates to a footwear tread which provides a high degree of traction on slippery surfaces and which is sufiiciently resilient to cushion the foot of the wearer.

It is well known in the prior art to construct a footwear tread having some degree of traction on smooth or slippery surfaces by providing a plurality of projections extending downwardly from the sole to engage the surface. Such a construction is exemplified by the disclosure of U.S; Patent No. 2,710,461 issued June 14, 1955. It has also been suggested to construct a footwear tread which would tend to resist slipping action in more than one direction by providing projections inclined in different directions in different areas of the tread. An example of such construction is that disclosed in Us. Patent No. 2,611,194, issued September 23, 1952. The degree of traction afforded by such footwear treads is generally proportional to the number of the projections per unit area. However, prior to the instant invention, it was not possible to increase the number of such projections without decreasing the size of the same below that considered to be a minimum for adequate traction on a given type of surface. Furthermore, such a decrease in size of the projections of the footwear tread had the result of impairing the ability of the tread to cushion the foot of the wearer when in use.

It is an object of this invention to provide a hightraction footwear tread having at least twice the number of projections possible in the constructions of the prior art without decreasing the size of such projections.

' It is a further object of this invention to provide a hightraction footwear tread having at least twice the number of projections possible in the constructions of the prior art without impairing the cushioning effect of such treads.

It is another object of this invention to provide a footwear treadwhich will'resist slippin g action in all directions regardless of which portiohof the tread is in contact with the walking surface.

It is another object of this invention to provide a footwear tread"having a maximum number of projections per unitai'eaof't'r'eadQ Other objects and advantages of this invention will be come apparent upon consideration of the following specification and claims when read in conjunction with the accompanying drawing "whereini A FIGURE l'is'a plan View of a footwear tread constructed in accordance with the teachings of this invention;

FIGURE 2 is a side view of the footwear tread illustrated in FIGURE 1 with the upper of the footwear omitted; and

Patent ed Jan. 30, 1962 resilient teeth integral with and projecting from the outer face disposed in a plurality of rows generally extending transversely and longitudinally of the tread, with every other tooth in each of the transverse rows pointing in opposite longitudinal directions, and with the teeth in each of the longitudinal rows pointing in the same longitudinal direction.

Referring to the drawing, and in particular FIGURE 1, there is shown a footwear sole 10 having a ball section 11 connected to a heel section 12. The connecte'd 'ball and heel sections are formed of a layer 13 of flexible resilient material. Such flexible resilient materials are well known in the footwear art as conventional sole and heel materials. Suitable materials will be seeri to include natural rubber, synthetic rubbers, such as polyurethane elastomers, and flexible resilient plastic materials such as polyvinyl chloride resin dispersions, conventionally designated as plastisols. Plastisols are liquid mixtures of thermoplastic resin particles in a liquid plasticizer having no substantial solvent action on the resin when cool, but capable of combining physically with the resin particles when the dispersion is heated to form a uniform mass of plasticized resin. The invention is not limited to 'anypar ticular material or class of materials, but includes any material which is flexible and resilient and which has sufficient wear-resistant properties to enable it to be employed as a footwear tread material. It should alsobe apparent that the novel tread of this inventionis not limited to use on a footwear sole having connected ball and heel sections, but is equally applicable to use as a tread for a heel per se or a sole having only a ball section without a heel section.

The present invention resides in a footwear tread, integral with and projecting from the outer face 14 of layer 13, comprising a plurality of teeth 15 formed from'a flexible resilient material. Preferably, the layer-'13 and the teeth 15 are formed from the same flexible resilient material in a single molding operation. As shown in FIGURE 1, the teeth 15 are disposed in a plurality of rows 16, 17 which generally extend transversely and longitudinally of the outer face 14. Forpurposes of this invention, the transverse and longitudinal rows, 16 and 17 respectively, need not form exact straight lines not need they be disposed on the exact transverse and longitudinal axes of the sole. As shown" in FIGURE 1,"the transverse rows 16 form a straightline whereas the longitudinal rows 17 take the form of a slight curve. In the transverse rows, every other tooth 18, 19 points in the opposite longitudinal direction, whereas the'teeth 18-, 26 in each of the longitudinal rows point in the same longitudinal direction. This construction affords a footwear tread which has a high degree of traction in all directions regardless of the portion of the tread in contact with the walking surface at any given instant.

The teeth may be adjacent to one another, but preferably are contiguous, particularly in the transverse rows 16, as shown in FIGURE 1 of the drawing. By contiguous 'is meant that the teeth have common boundaries. In the case of teeth having planar surfaces, contiguous teeth share a common side. Contiguous teeth are advantageous as there are no spaces in which foreign matter may lodge and thus a footwear tread having contiguous teeth maybe considered to he self-cleaning.

In the preferred form of'this invention, the teeth are polyhedral in shape and are essentially triangular in longitudinal cross-section. In order to provide teeth having an essentially triangular longitudinal cross-section, the polyhedral teeth 15 are selected from the group consisting of tetrahedral teeth, and pentahedral teeth, the latter being shown in FIGURES 1, 2 and 3 of the drawing. The pentahedral teeth are formed by truncating the vertex of tetrahedral teeth. As shown in FIGURES 1 and 2, a pentahedral tooth is formed by truncating the vertex of a tetrahedral tooth parallel to the edge which is the shortest distance to the base thereby forming an additional face at 21. The essentially triangular longitudinal cross-section of the teeth may be acute, obtuse or right triangular, the latter being preferred and shown in FIGURE 2 at 22. The phrase essentially triangular" is employed herein to include teeth which have a slight fiat plateau parallel to the base of the teeth at the points thereof, which plateau can be caused by wearing action at the points of the teeth or can be formed in the molding operation.

In order to have every other tooth in each of the transverse rows 16 pointing in opposite longitudinal directions and the teeth in each of the longitudinal rows 17 pointing in the same longitudinal direction, the slope of the hypotenuse 23 in longitudinal cross-section of each tooth should be approximately (-1) times the slope of the hypotenuse of the adjacent or contiguous tooth in the same transverse row and approximately (+1) times the slope of the hypotenuse of the adjacent or contiguous tooth in the same longitudinal row. Although it is not absolutely necessary, the base of all the teeth in a given transverse row should have the same longitudinal dimension. However, the longitudinal dimension of the base of the teeth in different transverse rows need not be the same. If the longitudinal dimension of the base of the teeth in different transverse rows are not equal, the vertical height of the teeth should be equal. In such a construction, the slope of the hypotenuse in longitudinal cross-section of a given tooth would not be exactly the positive of the slope of the hypotenuse of the adjacent or contiguous tooth in the same longitudinal row. Furthermore, even if the longitudinal dimension of the base of all the teeth in both the transverse rows and the longitudinal rows are equal, the slope of the teeth pointing in one longitudinal direction may be slightly greater than the negative of the slope of the teeth pointing in the opposite longitudinal direction if it is desired to afford a greater degree of traction in that one direction.

It is particularly advantageous to employ tetrahedral teeth, or pentahedral teeth of the shape shown in FIGURE 1, as this affords a maximum number of teeth or projections per unit area of tread and atfords twice as many teeth or projections per unit area without decreasing the size of such teeth or impairing the cushioning effect of the tread, as compared to a sole construction having such teeth pointing in only one direction.

In a tread construction wherein the teeth are relatively large, the longitudinal rows should contain an equal number of teeth and the transverse rows should contain an equal number of teeth. In such a construction, the longitudinal rows will contain from 5 to 15 teeth, whereas the transverse rows will contain from 3 to 9 teeth. In a tread construction wherein the teeth are relatively small, the longitudinal rows of teeth should extend in parallel straight lines with the transverse rows of teeth extending in parallel straight lines at right angles thereto. Such a construction will contain from 40 to 70 teeth in the longitudinal row of greatest length and from 15 to 30 teeth in the transverse row of greatest length.

The footwear tread of this invention can be molded and cured separately and thereafter adhered to an upper by a conventional cement. Another method of manufacture is to form the tread and adhere the same to the upper in a single injection molding operation. In the preferred method of manufacture, the tread is compression molded and adhered to the upper in a single operation. Actually, any satisfactory molding method can be employed as the footwear tread of this invention is not limited to the particular method of manufacture employed.

A typical composition for a tread which is molded and cured separately and thereafter adhered to the upper would be as follows, wherein the parts given are parts by weight:

Ingredient: Parts Natural rubber 100.0 Zinc oxide 1.0 Hydrated silicon dioxide 20.0 Zinc stearate 1.0

Wax 0.5 Polymerized dihydrotrimethylquinoline 0.1 Benzothiazyl disulfide 0.5 Z-mercapto benzothiazole 0.5 Zinc dimethyldithiocarbamate 0.25 Light parafiin oil 10.0 Sulfur 1.77

The above compound is placed in a two-part compression mold wherein the bottom part has the configuration of the tread and the top part is plain. A typical curing time is six minutes at 2000 p.s.i., with the bottom part of the mold at 307 F. and the top part of the mold at 287 F. After the tread has been molded and cured, it is adhered to the upper by any conventional adhesive.

A typical polyvinyl chloride plastisol composition for injection molding of the footwear tread is as follows, parts being given as parts by weight:

Ingredient: Parts Dicapryl phthalate 75.0 Dioctyl phthalate 10.0 Dipropylene glycol dibenzoate 10.0 Calcium carbonate 35.0

Polyvinyl chloride 100.0 Barium-cadmium salt stabilizer 2.0

The above composition is injected under pressure into a closed mold in which a lasted footwear upper has been positioned. The temperature is raised to 340 F. for four minutes to fuse the polyvinyl chloride plastisol and adhere the same to the shoe upper.

A typical composition for forming the footwear tread by compression molding and adhering the same to a shoe upper in a single operation is as follows, parts being given as parts by weight:

The above composition is placed in the cavity of a mold and a lasted upper is lowered into the top of the mold. The mold is then closed and the composition is cured under pressure for about seven minutes at about 290 F. whereby the tread is firmly adhered to the upper.

While the invention has been shown and described in a preferred form, it is to be understood that various changes and modifications may be made therein by one skilled in the art without departing from the principle of the invention, the scope of which is to be determined by the appended claims.

Having thus described my invention, what I claim and desire to protect by Letters Patent is:

1. A resilient footwear sole formed of a layer of flexible resilient material, said layer having an outer face, a plurality of flexible resilient teeth integral with and projecting from said face disposed in a plurality of rows generally extending transversely and longitudinally of the sole, every other tooth in each of the transverse rows pointing in opposite longitudinal directions, and the teeth in alternate longitudinal rows pointing in the same longitudinal direction.

2. A resilient footwear sole having connected ball and heel sections formed of a layer of flexible resilient material, said layer having an outer face, a plurality of flexible resilient teeth integral with and projecting from said face disposed in a plurality of rows generally extending transversely and longitudinally of the sole, every other tooth in each of the transverse rows pointing in opposite longitudinal directions, and the teeth in alternate longitudinal rows pointing in the same longitudinal direction.

3. A resilient footwear sole as defined in claim 2 wherein the longitudinal rows of flexible resilient teeth extend in parallel straight lines and the transverse rows of flexible resilient teeth extend in parallel straight lines at right angles thereto.

4. A resilient footwear sole as defined in claim 3 wherein the longitudinal row of greatest length contains from 40 to 70 flexible resilient teeth and the transverse row of greatest length contains from 15 to 30 flexible resilient teeth.

5. A resilient footwear sole as defined in claim 2 wherein the longitudinal rows contain an equal number terial, said layer having an outer face, a plurality of flexible resilient polyhedral teeth integral with and projecting from said face disposed in a plurality of rows generally extending transversely and longitudinally of the sole, the teeth in each of the transverse rows being adjacent and being essentially triangular in longitudinal cross-section with the slope of the hypotenuse of each of said teeth being approximately (l) times the slope of the hypotenuse of said adjacent teeth in the transverse row, and the teeth in alternate longitudinal rows pointing in the same longitudinal direction.

8. A resilient footwear sole having connected ball and heel sections formed of a layer of flexible resilient material, said layer having an outer face, a plurality of flexible resilient polyhedral teeth integral with and projecting from said face disposed in a plurality of rows generally extending transversely and longitudinally of the sole, the teeth in each of the transverse rows being adjacent and being essentially triangular in longitudinal cross-section with the slope of the hypotenuse of each of said teeth being approximately (-1) times the slope of the hypotenuse of said adjacent teeth in the transverse row, and the teeth in each of the longitudinal rows being adjacent and being essentially triangular in longitudinal cross-section with the slope of the hypotenuse of each of said teeth being approximately (+1) times the slope of the hypotenuse of said adjacent teeth in the longitudinal row.

9. A resilient footwear sole as defined in claim 8 wherein said polyhedral teeth are selected from the group consisting of tetrahedral teeth, and pentahedral teeth formed by truncating the vertex of tetrahedral teeth.

10. A resilient footwear sole formed of a layer of flexible resilient material, said layer having an outer face, a plurality of flexible resilient polyhedral teeth integral with and projecting from said face disposed in a plurality of rows generally extending transversely and longitudinally of the sole, the teeth in each of the transverse rows being continguous and being essentially right triangular in longitudinal cross-section with the slope of the hypotenuse of each of said teeth being approximately (1) times the slope of the hypotenuse of said contiguous teeth in the transverse row, and the teeth in each of the longitudinal rows being adjacent and being essentially right triangular in longitudinal cross-section with the slope of the hypotenuse of each of the said teeth being approximately (+1) times the slope of the hypotenuse of said adjacent teeth in the longitudinal row.

11. A resilient footwear sole having connected ball and heel sections formed of a layer of flexible resilient material, said layer having an outer face, a plurality of flexible resilient polyhedral teeth integral with and projecting from said face disposed in a plurality of rows generally extending transversely and longitudinally of the sole, the teeth in each of the transverse rows being contiguous and being essentially right triangular in longitudinal cross-section with the slope of the hypotenuse of each of said teeth being approximately (1) times the slope of the hypotenuse of said contiguous teeth in the transverse row, and the teeth in each of the longitudinal rows being adjacent and being essentially right triangular in longitudinal cross-section with the slope of the hypotenuse of each of said teeth being approximately (+1) times the slope of the hypotenuse of said adjacent teeth in the longitudinal row.

12. A resilient footwear sole as defined in claim 11 wherein the teeth in each of the longitudinal rows are contiguous.

13. A resilient footwear heel formed of a layer of flexiable resilient material, said layer having an outer face, a plurality of flexible resilient teeth integral with and projecting from said face disposed in a plurality of rows generally extending transversely and longitudinally of the heel, every other tooth in each of the transverse rows pointing in opposite longitudinal directions, and the teeth in alternate longitudinal rows pointing in the same longitudinal direction.

14. A resilient footwear heel formed of a layer of flexible resiilent material, said layer having an outer face, a plurality of flexible resilient polyhedral teeth integral with and projecting from said face disposed in a plurality of rows generally extending transversely and longitudi nally of the heel, the teeth in each of the transverse rows being contiguous and being essentially right triangular in longitudinal cross-section with the slope of the hypotenuse of each of said teeth being approximately (1) times the slope of the hypotenuse of said contiguous teeth in the transverse row, and the teeth in each of the longitudinal rows being adjacent and being essentially right triangular in longitudinal cross-section with the slope of the hypotenuse of each of said teeth being approximately (+1) times the slope of the hypotenuse of said adjacent teeth in the longitudinal row.

References Cited in the file of this patent UNITED STATES PATENTS 2,98l,0l1 Lombardo Apr. 25, 1961 

